Contribution of osteocalcin-mimetic peptide enhances osteogenic activity and extracellular matrix mineralization of human osteoblast-like cells

A natural peptide motif in the first helix of osteocalcin (OCN) is used to promote nucleation and crystallization of hydroxyapatite (HA) in hard tissue. The capability of osteocalcin mimetic peptides to induce osteogenic activity of osteoblast cells leading to in-vitro mineralization is demonstrated. An osteocalcin-derived peptide consisting of thirteen amino acids is synthesized in both acidic (OSC) and amidic (OSN) forms and added into the human osteoblast-like cells (MG63) culture. The viability, proliferation, alkaline phosphatase activity, HA deposition and osteogenic gene expression by osteoblast cells are evaluated. It is revealed that the addition of 100 mu g/ml of peptides enhances the proliferation rate and total protein content of osteoblast cells. Alkaline phosphatase activity is significantly higher in the presence of peptides which in turn stimulated RNA expression of collagen type I and osteopontin in a phosphate-dependent manner. Alizarin red staining and calcium content measurement show that mineral deposition is considerably increased. Ultrastructural characterization of MG63 cultures confirms the crystalline nature and chemical composition of HA mineral formation in the presence of peptides. It is confirmed that the osteocalcin-derived peptide, particularly in amidic form (OSN), is able to act as a bioactive inducer of mineralization process and hence accelerating bone tissue regeneration.